The present application is directed to methods of treating vertebral members and, more particularly, treatment methods using tethers with strength limits that prevent exertion of an excessive force on the vertebral members.
The spine is divided into four regions comprising the cervical, thoracic, lumbar, and sacrococcygeal regions. The cervical region includes the top seven vertebral members identified as C1-C7. The thoracic region includes the next twelve vertebral members identified as T1-T12. The lumbar region includes five vertebral members L1-L5. The sacrococcygeal region includes nine fused vertebral members that form the sacrum and the coccyx. The vertebral members of the spine are aligned in a curved configuration that includes a cervical curve, thoracic curve, and lumbosacral curve.
Various deformities may affect the normal alignment and curvature of the vertebral members. Scoliosis is one example of a deformity of the spine in the coronal plane, in the form of an abnormal curvature. While a normal spine presents essentially a straight line in the coronal plane, a scoliotic spine can present various lateral curvatures in the coronal plane. The types of scoliotic deformities include thoracic, thoracolumbar, lumbar or can constitute a double curve in both the thoracic and lumbar regions. Schuermann's kyphosis is another example of a spinal deformity that affects the normal alignment of the vertebral members.
One or more tethers may be attached to the vertebral members to reduce and/or eliminate the deformity. Tethering is often used with patients with growth potential, including prepubescent children less than ten years old who have yet to experience a growth spurt, and adolescents from 10-12 years old with continued growth potential. Generally, in the case of scoliosis, tethering takes place on the convex side of the curve. As the patient approaches puberty, the untethered side of the spine will grow unconstrained, ultimately eliminating the curvature of the spine in the coronal plane.